Resistance unit.



11. w. LEONARD. RESISTANCE UNIT.

APPLICATION FILED NOV. 13,1905.

Patented Nov. '2, 1909;

A Z i Q/mbneooeo w I v v H fJupm Ltoz g' 5 HARRY WARD nnounian, or Bnonxvrnsn, new "roan.

RESISTANCE UNIT.

Specification of Letters Patent.

Patented Nov. 2, 1909.

Application filed November 13, 1905. Serial No. 287,203.

To all whom it may concern:

Be it known that I, HARRY WARD LEON- niu'n'acitizen of the United States, residing at Bronxville, in the county of Westchester and State of New York, have invented certain new and useful Improvements in Resistance Units, of which the following is a full, clear, and exact specification.

My invention relates especially to electrical resistance units, such as might be advantageously used in the construction of rheostats, electric heaters and similar apparatus.

The principal object of myinvention is to improve the quality, reduce the cost and size, and produce a more commercial form of re.

' sistance units forgmany uses other than those heretofore known.

My invention is particularly well adapted for the use of resistance ribbons an overcomes the ditliculty that has been experienced in producing a substantial, tough, inexpensive form of apparatus, especially when the ampere capacity required for continuous duty is high, such for example as.

fifty amperes and upward.

By my present invention, I can readily produce a resistance capable of carrying continuously many hundreds of amperes and yet use for the purpose a ribbon so thin as to be so flexible by itself-as to be of little commercial value unless properly supported, insulated and protected. I can use ribbons of nickel copper alloy having a thickness of only one thousandth of an inch. Such resistance, material is very perfect from technical considerations and the use of such thin ribbon is very inexpensive for a certain wattdissipating capacity. By varying the thickness of the ribbon and by varying the width and length, a series of standard resistance units can be produced and these may be assembled by the user in .any. form, relation, and variety. to secure the result desiredby him. A resistance can' be expeditiously and economically produced which will have considerable. strength and be of any desired ohms, number .0 steps, ampere capacity,

- sha e and dimensions within desired limits.

and is therefore imited in its scope only as indicatedthe appended claims.

My invention will be understood from the following description and the accompanying drawings which show specific applications thereof.

Figure l is a side View of a resistance unit embodying my invention and comprising a refiexed'ribbon; Fig. 2 is a section on the line 22 of Fig. 1; Fig. 3 is a section on the line 3-3 of Fig. 1; Fig. 4; is a side View of a resistance unit which comprises a coil of wire; Fig. 5 is a section on line 5-5 of Fig. 4; Fig. 6 is a side view of a resistance unit in which a reflexed wire is employed; Fig. 7 is a section on the line 7-,7 of. Fig. 6; big. 8 is a side view of a modification which employs a reflexed ribbon; and Fig. 9 is a section on line 99 of Fig. 8.

Referring to Figs. 1 to 3 there is shown a thin reflexed ribbon 1. Extending over the edges of the ribbon are two supports 2, 2 which are preferably trough like in form and of sheet iron. The ribbon is embedded at its .edges in this instance in vitreous enamel 3 which serves to insulate the ribbon from the supports 2, 2, and also securely and rigidly connects the parts. I prefer to attach each end of the conductor to a support and in the present structure the supports 2, 2 are shown as having extenslons 4t, 4: respectively which are bent at right angles. One end of. the ribbon is secured by means of screws 5, nuts 6 and washers 7 to the part 4 of the support 2 and the other end of the ribbon is connected by similar electrically uniti g and. coupling up any number of such units as desired. In this construction,.the insulation is exposed to.

the voltage represented by the drop in volts upon the ribbon due to the passage ofthe current but this drop will usually be very low. The sheet iron supports serve to considerably increase the radiating, surface of the circuit and aid indissipatmg the heat. 7 Sometimes I use for the supports, fictile pieces such as pottery. Sometimes use insulation which is itself non-adhesive such as mica. If the support itself provides the necessary insulation, then separate insulation will be unnecessary. The supports may extend more or less over the sides of the ribbon so as to protect it from injury. The supports may sometimes be perforated. It will be seenthat the length of the resistance unit may be made anything desired within reasonable limits.

By using the thinnest ribbon of high grade alloys, I obtain at a very moderate cost the advantages of a resistance conductor of practically no temperature coeihcient, nonoxidizing in ordinary practice, having a very large current capacity and very low and permanent resistance.

While I prefer to support the ribbon at its edge, I can when desirable, have it supported upon its side surface, when it would have the appearance in side View of Fig. 6. In some forms I may use a metallic braid and if a ribbon is used I may perforate or slit it in order to vary its resistance.

While this invention at present seems most applicable to resistances of large current capacity, it may be applied to resistances which are intended to carry only small current. For example, Figs. 4 and 5 show a construction in which a coil of wire 8 is used as the conduct-or. The wire is embedded at opposite sides of the coil in insulation 3, such as vitreous enamel which also serves to rig idly unite the parts. The supports 9, 9 are here shown as having extensions 10 at the ends and provided with nuts and washers for coupling the units together mechanically and electrically using suitable insulation if electrical connection is not desired. The drawing shows one end of the wire 8 attached to one support at the end and the other end of the wire 8 attached to the other support. The drawing shows insulation at the ends of the support which do not have electrical connection and also indicates how additional units, the extensions 10 of which ally and-electrically in bank, each alternate terminal on each end being insulated and the other terminal being connected electrically.

Figs. 6 and 7 show a construction in which a wire conductor 8 is also used but is reflexed instead of coiled. vThis is embedded in suitable insulation'll which is .inclosed by the supports 12, 12. These supports have extensions 13, 13 to which the conductor is connected.

The supports may sometimes be held together by mechanical means so that an adesive attaching material is not necessary. For example, binding wires may be wrapped around the outside of the unit. Such a 'construction is shown in Figs. 8 and 9 in which the construction is in general similar to that of Fig. 1, except insulation of mica, asbestos, porcelain, etc, might. be us-ei'il beltween the edges of the ribbon and th supports. The binding wires '15 serve to Hold the parts firmly together and these should be insulated from the supports 2, 2 if the ribbon is connected electrically to the supports.

In some cases it will be desirable to embed the resistance unit in sand or some other medium having a high storage capacity for heat or having such properties as will still further protect the unit mechanically or electrically. A

Having thus described my invention, I declare that what I claim as new and desire to secure by Letters Patent, is,

1. The combination of'a reflexed ribbon conductor, and two protective sheet metal supports, the said ribbon being supported edgewise between said supports and the opposite terminals of said conductor being electrically connected to said supports respec tively. 2. The combination of a resistive conductor, two supporting members therefor supporting said conductor between them, and means for insulating said members from each other and from said conductor and for adhesively attaching the parts to 'ether, the opposite ends of said resistance being electrically connected to said two members respectively.

3. in a resistance unit, the combination of a resistance, and supporting-means therefor comprising sheet metal elements supporting said resistance between them and an adhesive coating of mineral insulating material for insulating the parts, the said elements being electrically connected together by said resistance.

l. In a resistanceunit, the combination of a flexible metallic ribbon, two rigid supports therefor, means for adhesively attaching said supports to opposite edges of said ribbon respectively to form a rigid structure, and circuit terminals for said ribbon carried by said supports respectively.

5. In a resistance unit, the combination of a resistance, two protecting and supporting members between which said resistance is 4 held so as to be 0 only exposed to the free emission of heat y radiation and convection, and circuit terminals carried by said members and to which the opposite ends of said resistance are connected respectively.

'6. In a resistance unit, the combination of two metal supporting members, a resistance between said members openly exposed to the freeemission bf heat by radiation and convection, means adhesively attaching said resistance to said members while insulating said members therefrom, and means" for electrically' connecting the two ends of said resistance with said members respectively.

7. In a resistance unit, the combination of two trough-shaped members, a resistance bettv'ee'n seid; members openiy' exposed to the a In testimony whereof I aflix my signature, free GIIllSSlOIl of heat by radiatlon and con- 1n presence of two wltnesses. vectlon, means sdhesively attaching said resistance to said members While insulating WARD D 5 said members therefrom, and means for elec- Witnesses:

trically connecting the two ends of said re- CAROLYN G. LEONARD,

sistance with said members respectively. I SARAH MCDONALD. 

